Sebuku Coal Mine, Indonesia

The coal seams of Sebuku Island occur within the lower part of the Eocene Tanjung formation. The coal seams are preserved within a number of deposits in the south-west region of Sebuku Island.
The main deposit is preserved within a broad north-south trending syncline that is truncated along the eastern boundary by the major Kanibungan Fault. The flanks of the syncline dip gently at typically less than 10°.
The Tanah Putih deposit lies to the northwest of the main deposit and fills a basin that deepens and thickens to the west. Further seams are developing at depth and thickening to the west above the ultramafic basement.
The strata consist predominantly of weak mudstone and shale with interbedded coal seams. All strata are capable of being mined without the need for blasting.
The coal is of high volatile bituminous rank with an average in-situ ash of 12%, total sulphur of 1.05%, a calorific value of 6,085KCal/kg (air-dried basis) with an average in situ total moisture of 14%. The coal is typically lustrous with occasional bright bands.